It is commonplace today to generate metallic patterns or deposits on electrically insulative or dielectric surfaces by means of electroless metal deposition techniques. Conventionally, aqueous sensitizer solutions are employed wherein a catalytic species is deposited on the surface which catalyzes electroless metal deposition from a suitable electroless metal deposition solution. Where the surface to be metallized is hydrophobic, as for example in the case of most organic polymeric substrate surfaces, it is often very difficult to achieve wetting thereof by the conventional aqueous sensitizer solutions thereby leading to electroless metal deposits which are discontinuous and/or have poor adhesion to the surface metallized.
One such prior art technique is disclosed in U.S. Pat. No. 3,993,491. Here, surfaces of dielectric substrates are catalyzed for electroless metal deposition thereon by treating the substrate with aqueous solutions containing stannous and copper ions in the form of a soluble complex and then with a chemical reducing agent capable of reducing cuprous ion to the metallic state. The compositions set forth in this patent are aqueous solutions and not wetting colloidal dispersions. These solutions are generally formed under highly acidic conditions in solutions having relatively high concentrations of stannous ion as compared to the wetting colloids of the present invention. Further, there appears to be no criticality as to the method or sequence of preparing the final solution taught by this patent.
A method of electrolessly depositing a metal on hydrophobic surfaces with a continuous and adherent metal deposit is desired and needed.